Put your code in a variable and eval it.

$end = 0;
$var = 1;
$code='print "test $code";
$end = 1 if ($var >= 2);
$var++;
eval ($code) if ($end == 0);';
eval($code);
[download]

This will let you modify your code (I didn't modify mine, but it gives you an idea of how to do it).
PS. Opening a file is much safer, easier, and better coding practice.